Tachycardia is a type of cardiac arrhythmia and is a serious, often-times, fatal condition characterized by rapid, uncontrolled, and ineffective beating of the heart. Most tachycardia is one of two broad categories: ventricular tachycardia (hereinafter VT) and supraventricular tachycardia (hereinafter SVT). VT occurs in the lower chambers of the heart, the ventricles, and frequently leads to serious complications, including sudden cardiac death. Atrial fibrillation and flutter, forms of SVT, originate in the upper chambers of the heart, the atria, and often result in chest pain, fatigue and dizziness and, while generally not life-threatening, is a leading cause of stroke in the United States.
Currently, many cases of VT and SVT are treated by drugs that modify the electrical characteristics of the heart tissue. However, the drugs do not eliminate or may not completely control the arrhythmia. In many cases of sustained VT, implantable cardiac defibrillators are used which deliver powerful shocks to the heart when fibrillation is detected. Concurrent treatment with drugs is standard therapy and each implantation of a cardiac defibrillator, of which there may be more than one per patient, is very expensive.
Some forms of SVT are treated by endocardial ablation, a minimally invasive procedure. During endocardial ablation, a mapping catheter is passed through an artery or vein into the patient""s heart to find the site(s) of the arrhythmogenic tissue, the tissue from which the tachycardia originate. This same catheter or a separate catheter is used to transmit sufficient energy to thermally damage the tissue either by heating or cooling. (FIG. 1)
In atrial fibrillation the regular pumping action of the atria is replaced by a disorganized, ineffective quivering caused by chaotic conduction of electrical signals through the upper chambers of the heart. Although not immediately life threatening, atrial fibrillation may cause up to a 30% reduction in cardiac output and can lead to more serious conditions, including the formation of blood clots in the atria that can dislodge and travel to the brain resulting in stroke. Currently, the only curative treatment for atrial fibrillation is the surgical xe2x80x9cmaze procedurexe2x80x9d, an open heart procedure in which the surgeon makes several incisions in the right and left atria creating scar tissue to electrically separate portions of the atria. Despite clinical success of the maze procedure, it is time-consuming and demanding. The procedure requires open heart surgery and is very expensive. Accordingly, only a modest number of maze procedures are performed annually in a limited number of centers.
Another use of ablation technology, either endocardial or epicardial, is transmyocardial revascularization. The creation of small ablation holes results in genesis of new blood vessels, providing a source of blood flow in areas of the heart not receiving sufficient blood.
The present invention provides another apparatus and method for treating cardiac arrhythmia, that may be widely applicable. The present invention also provides an apparatus for transmyocardial revascularization.
The present invention provides devices and methods for epicardial and endocardial approaches for myocardial ablation for treatment of cardiac arrhythmias and myocardial revascularization.
One aspect of the invention provides a gripper for grasping the epicardial surface of the heart for the purpose of ablating cardiac tissue. In one embodiment, the arms of the gripper are sized and dimensioned to substantially encircle the circumference of the heart or a portion of it, thereby stabilizing the gripper against the contracting heart. The ablators are sized and positioned on one or more of the arms of the gripper according to the location and geometry of the cardiac tissue to be ablated.
In another embodiment, the gripper is sized and dimensioned to encompass structures on the surface of the heart. In yet another embodiment of this aspect of the invention, one arm of the gripper is inserted through an incision in the wall of the heart into one of the heart chambers. The other arm or arms of the gripper are positioned on the epicardial surface to stabilize the heart. The ablators are located on an arm or arms in an array according to the location and geometry of the tissue to be ablated. In one embodiment, the gripper ablates both the epicardial and endocardial surfaces.
In one embodiment, one or more of the arms may form an array. One embodiment of the array is a Y. Another embodiment of the array are loops or spokes.
Another aspect of the invention is an electrode system comprising a probe in the form of an adjustable, flexible substrate forming a substantially closed loop for epicardial ablation. In one embodiment of the invention, the loop is sized to substantially encompass a structure on the epicardial surface of the heart. In another embodiment, the loop is substantially sized to encircle the circumference of the heart. The cross section of the probe may be round, oval, multifaceted or have multiple radii. In one embodiment the probe does not encompass the entire circumference of a portion of the heart.
In another embodiment of this aspect of the invention, the size of the substantially closed loop comprising the probe is adjustable by a pull string attached to one end of the probe. In another embodiment the probe substrate comprises an elastomeric material. The loop of the elastomeric probe is adjustable by expanding or contracting the probe.
In another embodiment of this aspect of the invention, the electrode system is sized and dimensioned for insertion through an endoscope or thoracoscope. In yet another embodiment, the electrode system includes attachments such as, for example, a cooling system in communication with the probe or a gripping device such as a suction device in communication with the probe.
In one particular embodiment of the invention, the electrode system comprises a glove and an ablator in communication with one or more fingers of the glove.
The ablators of the electrode system are positioned generally to correspond to the cardiac tissue to be ablated. In one embodiment, the ablators are positioned on the inner surface of the probe. In another embodiment, the ablators are positioned on more than one surface of the probe. For example, the ablators may be positioned on the flat surface of a probe with a D-shaped cross section, on one semi-circle of a circular cross section, or on one or more surfaces of a rectangular cross section. The ablators may be located on one or more arms in any configuration.
In a preferred embodiment of this aspect of the invention, the ablators may be individually and independently activated. In another particular embodiment, the ablators are removably attached to the probe substrate.
Another aspect of this invention comprises an endocardial ablator-detection and ablation system for performing transmyocardial ablation. The ablator-detection and trans-myocardial ablation system provides an indicator located on an endocardial ablating catheter adjacent an ablator, and a detector located on an epicardial probe. The indicator located on the endocardial ablating catheter transmits a signal indicating the position of the ablator on the catheter. The epicardial detector receives the signal thereby localizing the relative epicardial position of the ablator on the endocardial catheter. Ablating energy is applied when the ablator is appropriately positioned.
In one embodiment of the endocardial ablator detection system, the indicator is a magnet and the detector is a magnetic field detector. In another embodiment of the detection system, the indicator is a light transmitter, such as, for example, laser light, and the epicardial detector comprises a light detector. In another embodiment of the system the indicator is a light source emitting fluorescent light and the epicardial detector detects light in the wavelength of fluorescence. In yet another embodiment of the invention, the epicardial detector comprises an ultrasound detector, or an echocardiograph. In yet another embodiment, a magnet in the epicardial probe attracts a magnetic or metallic element in the endocardial ablator, guiding the ablators into position.
In any aspect of the invention, cooling or ablating energy may be applied by the ablators to ablate cardiac tissue. In one embodiment, cooling fluid travels via a lumen in the ablator and exits via small holes carrying the fluid through another lumen that exits from the catheter. The change in pressure or phase change results in cooling or freezing. The ablating energy applied to ablate cardiac tissue in any aspect of the invention may be thermal, radio frequency, direct current, ultrasound or laser energy.